A gas turbine includes an inlet section that allows air intake into the gas turbine, and a compressor section that includes rotor and stator wheels, which draw in and compress air to be mixed with fuel in a combustor section downstream of the compressor section. Combustion gases generated in the combustor sections are used to turn turbine wheels in the turbine section to generate power. Located on the compressor rotor and stator wheels, gas turbine compressor blades are placed such that the blades are exposed to the inlet air and the heat produced during operation of the compressor. The compressor blades include an airfoil section that aids in drawing and compressing inlet air, and a root section that keeps the blades on the compressor wheels.
During operation, compressor blades may be exposed to corrosion. Out of the major sections of a compressor blade, the airfoil section of the compressor blade is the most exposed section to the harsh environment, and is most susceptible to damage.
There is a continuing desire to improve airfoil efficiency and durability of a compressor blade. Conventionally, the compressor blade is made up of a single material selected to fulfill airfoil performance requirements for durability and efficiency. The material ideally has the ability of coping with erosion, corrosion, and fatigue of the blade over time. However, some regions of the airfoil may require additional strengths and/or different physical properties than other regions on the airfoil. For example, the leading edge of the airfoil may endure more erosion and corrosion than the trailing edge, and other areas may require a material having a higher strength than the leading edge.
Attempts to solve the problem of having different requirements on different regions of the airfoil portion include providing airfoils with different coatings of material to solve corrosion and/or erosion issues. However, coatings may not be the optimal solution to the problem of enduring different regional issues since some coatings are normally applied to the airfoil portion as a whole. Coatings may also have potential crevice corrosion or material interface compatibility issues between the layers of coatings.
In addition, a material that may provide the optimal durability, erosion, corrosion, strength, and efficiency for all regions on an airfoil of the compressor blade may not be economically feasible for manufacturing and use in an industrial gas turbine. Accordingly, there is a need for an improved blade that can efficiently fulfill localized airfoil performance requirements such as erosion, strength, corrosion, and fatigue capability. The present invention provides a solution for (or presents an alternative to solve) the compressor blade airfoil durability issues described.